81197631 has 12 divisors (see below), whose sum is σ = 120013608. Its totient is φ = 52872624.

The previous prime is 81197603. The next prime is 81197657. The reversal of 81197631 is 13679118.

81197631 is a `hidden beast` number, since 8 + 1 + 19 + 7 + 631 = 666.

It is not a de Polignac number, because 81197631 - 2⁷ = 81197503 is a prime.

It is a super-2 number, since 2×81197631² = 13186110560024322, which contains 22 as substring.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81190631) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 104520 + ... + 105293.

It is an arithmetic number, because the mean of its divisors is an integer number (10001134).

Almost surely, 2^81197631 is an apocalyptic number.

81197631 is a deficient number, since it is larger than the sum of its proper divisors (38815977).

81197631 is a wasteful number, since it uses less digits than its factorization.

81197631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209862 (or 209859 counting only the distinct ones).

The product of its digits is 9072, while the sum is 36.

The square root of 81197631 is about 9010.9728109677. The cubic root of 81197631 is about 433.0264781565.

The spelling of 81197631 in words is "eighty-one million, one hundred ninety-seven thousand, six hundred thirty-one".